This invention relates to optical couplers and, more particularly, to optical couplers for coupling light between a fiber-optic and a planar waveguide.
Recent developments in optical communications have provided low-loss fiber-optic waveguides, which are employed as transmission lines, and thin-film planar optical waveguides for performing optical processing, such as switching, modulation, etc. This has provided a need for improved optical couplers for coupling light between the fiber-optic and the planar waveguide. An example of one such optical waveguide coupler is disclosed in my U.S. Pat. No. 3,912,363, issued Oct. 14, 1975, and assigned to the same assignee as the present application.